CN108072887A - Single base station marine real-time dynamic positioning method at a distance - Google Patents
Single base station marine real-time dynamic positioning method at a distance Download PDFInfo
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- CN108072887A CN108072887A CN201711083653.0A CN201711083653A CN108072887A CN 108072887 A CN108072887 A CN 108072887A CN 201711083653 A CN201711083653 A CN 201711083653A CN 108072887 A CN108072887 A CN 108072887A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/38—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system
- G01S19/39—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/42—Determining position
- G01S19/421—Determining position by combining or switching between position solutions or signals derived from different satellite radio beacon positioning systems; by combining or switching between position solutions or signals derived from different modes of operation in a single system
- G01S19/425—Determining position by combining or switching between position solutions or signals derived from different satellite radio beacon positioning systems; by combining or switching between position solutions or signals derived from different modes of operation in a single system by combining or switching between signals derived from different satellite radio beacon positioning systems
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/38—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system
- G01S19/39—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/42—Determining position
- G01S19/43—Determining position using carrier phase measurements, e.g. kinematic positioning; using long or short baseline interferometry
- G01S19/44—Carrier phase ambiguity resolution; Floating ambiguity; LAMBDA [Least-squares AMBiguity Decorrelation Adjustment] method
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Abstract
The present invention provides a kind of methods of single base station marine real-time dynamic positioning at a distance, the differential corrections after simplifying are transferred using the short message function of triones navigation system, solve the problems, such as marine communication inconvenience even without communication, recycle the Big Dipper and a variety of observations of multiple frequencies of two satellite navigation systems of GPS, for marine particular surroundings, develop stabilization, quickly, accurately flow the real-time location algorithm in end, finally realize corresponding base station correction player software and the real-time positioning software of rover station, a set of long range sea real-time dynamic positioning system based on single base station is built.
Description
Technical Field
The invention relates to the field of GNSS precision positioning, in particular to marine remote high-precision real-time dynamic positioning.
Background
Since the advent of the GPS system, the Global Navigation Satellite System (GNSS) has been widely used in various outdoor positioning and navigation applications. Real-time high-precision positioning is an important research field of GNSS. Currently, real Time Kinematic (RTK) technology, precision Point Positioning (PPP) technology, and their extended network RTK technology and PPP-RTK technology are representative of high precision GNSS positioning technologies. However, these techniques have their own drawbacks in offshore applications.
PPP technology requires precise ephemeris, clock, etc. that are released at a delay of about one week on a particular web site. As for the real-time ephemeris and clock services provided by some ultrafast ephemeris and IGS (International GPS Service), it is difficult to obtain the services in real time in the open sea environment. In fact, most of the real-time PPP techniques currently only implement algorithmic real-time, but are not put into practical use, and only simulate real-time conditions in post-processing. In addition, some existing commercial software capable of providing real-time precise positioning service in the global scope mainly transmits some correction information through satellite communication, and the cost is high and only the positioning precision of the decimeter level can be maintained. It can be seen that although real-time PPP technology can theoretically and experimentally achieve real-time precise positioning in open sea or even in the world, in practical applications, there are some problems to be solved.
The single station effective service range of the current RTK technology theory can reach 100 kilometers or more. On the premise of not considering the fixed ambiguity, the requirement on the precision is properly relaxed, and the single station service range of the RTK can be further expanded to hundreds of kilometers. This means that high-precision real-time dynamic positioning can be provided for sea areas ranging over hundreds of kilometers along the sea in theoretical mountains using RTK technology. In fact, due to the limitation of communication means, in the environment of open sea without network, the correction number is transmitted by radio waves sent by a radio station, and the effective transmission distance is only about thirty kilometers, so that the single station service range of RTK can not reach the limit distance of RTK.
RTK seems to be less suitable for marine positioning than PPP. PPP technology, however, is not only limited by communication conditions, but also requires expensive hardware network infrastructure support. In addition, the single station service range of the RTK technology can meet the requirements of many offshore applications in the open sea if the service range can reach hundreds of kilometers. Therefore, if the communication problem can be solved properly, the RTK technique is more suitable for high-precision navigation at sea because of less expenditure and simple construction. However, there are many problems to be solved in realizing high-precision real-time dynamic positioning at sea in a single station service range of hundreds of kilometers by using the RTK technology.
Disclosure of Invention
The applicant has found that satellite communication is a viable solution to the marine communication problem. However, the cost of satellite communication is expensive, and compared with the cost of service of Beidou short message communication, the service cost of Beidou short message communication is much cheaper, but the bandwidth of Beidou short message communication is very small, and the amount of information which can be transmitted at one time is very limited. If the correction information needing to be transmitted is not simplified and compressed, the Beidou short message can not be used for transmitting the correction information. However, when simplifying the correction number information, it is necessary to avoid adverse effects on the positioning effect of the mobile station as much as possible. Therefore, how to use the beidou short message to transmit the correction information of the reference station and not to influence the positioning effect of the rover station is an important problem.
Further research by the applicant finds that, at sea, the observation environment is different from the land, the multipath effect is obvious, and the equipment needs to be arranged on a ship, and the ship often has some other equipment to interfere with the satellite signal, so that the rover observation data obtained in the environment often has several gross errors. For single gross errors, it can be better detected in single point positioning using correlation analysis. However, for two or more gross errors, because the number of redundant observations in satellite positioning is small, the effect of gross error detection is poor, and the situations of erroneous judgment and missed judgment often occur. Therefore, how to reduce the influence of multiple gross errors on the positioning result as much as possible is a problem to be solved by the rover station positioning algorithm.
In order to solve the above problems, the present invention aims to provide a method and a system for single-base-station remote marine real-time dynamic positioning, which utilize the beidou short message to transmit the correction information and consider the marine special observation environment, so as to meet the positioning requirements of various marine engineering projects.
In order to achieve the purpose, the invention provides a single-base-station long-distance marine real-time dynamic positioning method, which comprises the following steps:
and receiving the RTCM format data stream of the reference station in real time at the server side, and decoding the RTCM format data stream to obtain ephemeris data and real-time observation data of the current epoch. And preprocessing the data, and removing unqualified observation data. And then, simplifying the observation data by using a simplified correction number algorithm, thereby obtaining a simplified correction number.
Judging whether the simplified correction number calculated by the current epoch meets the requirement, if so, performing ASCII encoding on the correction number and entering an observation data processing flow of the next epoch; otherwise, the simplified correction number of the current epoch is discarded and the observation data processing flow of the next epoch is entered.
And packaging and splitting the coded simplified correction number into a plurality of short messages, submitting the short messages to a Beidou short message antenna of the service end for sending, sequentially receiving a plurality of Beidou short messages sent by the service end antenna by the Beidou short message antenna of the user end, and splicing the short messages into the coded simplified correction number again for being used by user end positioning software.
The user terminal positioning software needs to receive the RTCM format data stream of the mobile station and the simplified correction number after the coding sent by the short message antenna at the same time. And reading the observation data of the ephemeris and the current epoch rover from the data stream, and preprocessing the data to remove unqualified observation data. Decoding the encoded simplified correction number, judging whether the simplified correction number is qualified, and if so, performing offshore real-time kinematic (Ocean-RTK, ORTK) positioning; otherwise, only single point positioning is performed. And finally, after the positioning result is spitted out, entering the observation data processing flow of the next epoch.
Preferably, the step of preprocessing the reference station observation data and the user side data includes single-point positioning, pseudo-range observation value checking and rough error detection by a correlation analysis method. And the pseudo-range observation value checking refers to that the known reference station coordinates or the predicted user terminal rover station coordinates and satellite coordinates resolved in ephemeris are used for reversely deducing corresponding satellite distances so as to be compared with corresponding pseudo-range observation values, and if the difference between the pseudo-range observation values and the reversely deduced satellite distances is large, the observation values are considered to contain gross errors and should be discarded. The coarse difference detection by the correlation analysis method is to analyze coarse differences possibly contained in an observed value by using a coarse difference theory based on the correlation analysis after obtaining an observed value residual error sequence through single-point positioning, and abandon the observed value if detecting that the observed value contains the coarse differences.
Preferably, the step of simplifying the observation data by using the simplified correction algorithm includes deducting the computed satellite-earth distance from the original observation value, and eliminating a geometric distance variation term generated due to the satellite motion in the observation value; and then deducting the model correction quantity of troposphere delay in the observed value, reducing the numerical change of the original observed value as much as possible, and simultaneously reducing the absolute value of the pseudo-range observed value as much as possible, wherein the calculation formula is as follows:
wherein, the first and the second end of the pipe are connected with each other,and withIs the corrected phase and pseudorange observations,andis the raw phase and pseudorange observations, the subscript r represents the reference station, the superscript s represents a satellite,andthe satellite earth distance, the receiver clock error and the satellite clock error calculated for the single-point positioning,the amount is modified for the model of tropospheric delay.
Finally, deducting the rounded integer part from the phase observed value and only keeping the decimal, so that the phase observed value only takes values from-0.5 to 0.5, and the calculation formula is as follows:
wherein the content of the first and second substances,is a phase reduced observed value [. Alpha. ]]Denotes rounding the sum of x, λ is the observed phaseThe corresponding wavelength. In practice, integers areObserved value in phaseThe cycle can be used without cycle skipping and without recalculation each time.
The observations in the resulting simplified corrections include, after correction, pseudorange observationsAnd phase reduced observations
Preferably, the criterion for determining whether the simplified correction calculated by the current epoch meets the requirement is to determine whether the absolute value of the pseudorange or the phase observation exceeds 1000, and if not, the simplified correction meets the requirement, otherwise, the simplified correction does not meet the requirement.
Preferably, the ASCII encoding of the modified number means that all the simplified modified number information including the modified number observation time, the system flag, the satellite number, the simplified observed value, etc. is converted into a binary form, and then the simplified modified number information in the binary form is converted into an ASCII character string form for transmission. For example, when 3 binary bits are used to represent the form of the system flag as 1 as 001, 5 binary bits are used to represent the form of the satellite number as 8 as 01000, and the information of the system flag and the satellite number is combined as 00101000, the converted information is converted into ASCII characters as '40'. The specific coding method comprises that the 0 th bit to the 9 th bit of the binary correction number are used for storing the last three bits of the observation time of the simplified correction number, the 10 th bit to the 12 th bit are used for storing a system mark, and the 13 th bit to the 17 th bit are used for storing satellite numbers; store information for each observed satellite starting at bit 18, 6 bits for storing satellite number, 5 bits for storing satellite ephemeris time, 1 bit for storing satellite ephemeris timeThe flag of whether to change, 21 bits, is used to store an observation of phase or pseudorange. After the binary number is obtained, every 8 bits can be converted into an ASCII character, and finally, less than 8 bits are converted into the ASCII character after 8 bits are filled with 0.
Preferably, the step of packaging and splitting the encoded simplified correction number comprises dividing the simplified correction number information into a plurality of short messages, wherein each short message needs to be added with a check symbol to ensure that the messages can be recovered at a user terminal, and meanwhile, the size of each short message cannot exceed the maximum data volume which can be sent by a Beidou short message antenna at a service terminal at one time.
Preferably, the step of splicing the received big dipper short messages into the coded simplified correction number by the user side includes checking whether the received short messages belong to the same simplified correction number information or whether the short messages of the same simplified correction number information are missing or not by using a check symbol of each short message, and after checking, if the problem does not exist, splicing the short messages belonging to the same simplified correction number information in sequence according to the check symbol to obtain a complete piece of coded simplified correction number information, otherwise, waiting until all the short messages of the simplified correction number information are received by the user side.
Preferably, the method for judging whether the simplified correction number is qualified at the user side is to calculate the difference between the observation time of the simplified correction number and the observation time of the observation data of the rover station, if the time difference is less than 1 minute, the simplified correction number is qualified, otherwise, the simplified correction number is unqualified.
Preferably, the ORTK positioning of the rover station is performed based on Ionosphere-Free (IF) combination of dual-frequency phase and pseudorange observed values of two navigation systems of GPS and beidou, and the method includes the steps of constructing an inter-station differential observed value by using rover station observed data and a received simplified correction number, and the formula is as follows:
wherein, the first and the second end of the pipe are connected with each other,andfor simplifying the observed values of differential phase and pseudo range between stations,andis a phase simplified observed value of a reference station and a corrected pseudo range observed value,andfor the raw phase and pseudorange observations of the rover station,andapproximate satellite distance, receiver clock error and satellite clock error of the rover calculated by single-point positioning,the rover is modeled on the tropospheric delay.
After the inter-station difference observation value is obtained, selecting a proper reference satellite, and carrying out inter-planet difference to obtain a double-difference observation value, wherein the formula is as follows:
wherein the superscript s represents the selected reference satellite and the superscript v represents any other satelliteAnd withRepresenting simplified double-differenced phase and pseudorange observations,and withRepresenting simplified post-station differential phase and pseudorange observations of satellite v.
Then, considering that the observed value has two frequencies, a linear combination can be performed on the dual-difference observed values of the two frequencies to obtain a dual-difference observed value of the IF combination, where the following formula is shown:
wherein the content of the first and second substances,anddouble differential observation of phase and pseudoranges for IF combining 1 Frequency of the first frequency observation, f 2 For the frequency of the second frequency observation,andis a dual differential observation of the phase of the first frequency and the pseudorange,andthe phase and pseudorange dual differential observations for the second frequency.
Because residual tropospheric delay is not considered, the only parameters to be solved based on the IF combined double-difference observations are the rover position parameters and the IF combined double-difference ambiguity parameters, an error equation as shown below can be obtained:
wherein, the first and the second end of the pipe are connected with each other,is a double-difference earth distance, and comprises three unknown rover position parameters,is the wavelength of the narrow lane, c represents the speed of light,for the IF combining of the double-difference ambiguity parameters,and withAre the residual phase and pseudorange observations errors.
Writing the error equation in matrix form:
wherein phi IF And P IF An observation vector composed of a plurality of satellite phase and pseudo-range double-difference observations, A is a coefficient matrix of the position parameters of the rover station, I m Is an m-order identity matrix, m is the number of ambiguity parameters, x represents the rover's position parameter vector, a represents the ambiguity parameter vector,and withIs an error vector formed by the residual errors.
The rover position parameter is different due to the motion of the rover every moment, but the ambiguity parameter does not change along with the time, so that the characteristic can be utilized to combine the observed value information of a plurality of moments for sequential calculation. In the sequential solution, the calculation formula of the rover position parameter and the ambiguity parameter is as follows:
wherein, the first and the second end of the pipe are connected with each other,and withRespectively obtaining errors in prior of two frequency original phases and pseudo-range observed values; q dd The covariance matrix is a covariance matrix of double-difference observed values and is independent of frequency;andcovariance matrices of pseudo-range and phase double-difference observations of the IF combinations, respectively; the subscript k represents the time of day,and A k Respectively representing ambiguity parameter solutions at the k moments, rover position parameter solutions and coefficient matrixes of rover position parameters;is a covariance matrix of the ambiguity parameter solution at the time k;is a covariance matrix of the rover position parameter solution at the time k; when k =0, the number of the bits is set to zero,andis a zero vector or a zero matrix.
Preferably, the ORTK positioning of the rover station is different from the conventional RTK positioning, which needs to additionally consider the observation time inconsistency of the rover station observation data and the simplified correction number and the problems of serious marine multipath effect and special observation environment. Since the satellite clock differences cannot be eliminated by the inter-station difference due to the inconsistency between the observation data and the observation time of the simplified correction number, the accurate satellite clock differences at the respective observation times must be calculated by using the ephemeris of the satellites at the time of single-point positioning, and then subtracted from the original observation values as shown in equations (1 a) and (1 b). And, it must be ensured that the rover and the reference station use the same time satellite ephemeris for the calculation of the satellite clock error. In the sea, the observation environment is different from the land, the multipath effect is obvious, and the equipment needs to be arranged on a ship, and the ship often has some other equipment to interfere with the satellite signal, so that the rover observation data obtained in the environment often contains a plurality of gross errors. For single gross errors, correlation analysis can be used to better detect in single point locations. However, for two or more gross errors, because the number of redundant observations in satellite positioning is small, the gross error detection effect is poor, and the situations of erroneous judgment and missed judgment often occur, at this time, because the ORTK positioning is based on sequential solution, the parameter solution quality at all subsequent times can be influenced by the failure of gross error detection at a certain moment. In order to avoid the situation, the ORTK not only adds the correlation analysis method coarse difference detection in single-point positioning, but also utilizes pseudo-range double-difference observed values combined by IF (intermediate frequency) to carry out positioning and coarse difference detection in subsequent ORTK positioning, and checks the posterior-to-intermediate error of parameters obtained by resolving the final ORTK positioning. If the gross error detection fails, the error in the parameter after test is obviously larger and even exceeds the normal value by several orders of magnitude, and at the moment, the moment is skipped without updating the result into the parameter of sequential calculation, and the moment gives out the result of single-point positioning.
In the single-base-station long-distance offshore real-time dynamic positioning method provided by the invention, firstly, a reference station RTCM format data stream is received in real time at a server side and decoded to obtain ephemeris data and current epoch real-time observation data. And preprocessing the data, and removing unqualified observation data. And then, simplifying the observation data by using a simplified correction number algorithm so as to obtain a simplified correction number. Then judging whether the simplified correction number calculated by the current epoch meets the requirement, if so, performing ASCII encoding on the correction number and entering the observation data processing flow of the next epoch; otherwise, the simplified correction number of the current epoch is abandoned and the observation data processing flow of the next epoch is entered. And then packaging and splitting the coded simplified correction number into a plurality of short messages, submitting the short messages to a Beidou short message antenna of the service end for sending, sequentially receiving a plurality of Beidou short messages sent by the service end antenna through the Beidou short message antenna of the user end, splicing the short messages into the coded simplified correction number again, and submitting the coded simplified correction number to user end positioning software for use. The user positioning software needs to receive the RTCM format data stream of the mobile station and the code simplified correction number sent by the short message antenna at the same time. And reading the observation data of the ephemeris and the current epoch rover from the data stream, and preprocessing the data to remove unqualified observation data. Decoding the encoded simplified correction number, judging whether the simplified correction number is qualified, and if so, performing offshore real-time kinematic (Ocean-RTK, ORTK) positioning; otherwise, only single point positioning is performed. And finally, after the positioning result is spitted out, entering the observation data processing flow of the next epoch. The invention solves the problem of inconvenient marine communication by using the Beidou short message; the simplified correction algorithm and the corresponding coding method are utilized to solve the problems that the Beidou short message communication bandwidth is too small and is not suitable for transmitting normal correction information; by utilizing the method of multiple coarse error detection and error detection after inspection, the continuous deterioration of the positioning effect is avoided as much as possible under the condition of multiple coarse errors, so that the positioning algorithm of the user terminal rover station can adapt to the special environment at sea.
Drawings
Fig. 1 is a flowchart of a single-base-station long-distance offshore real-time dynamic positioning method in an embodiment of the present invention.
Detailed Description
The following describes in more detail embodiments of the present invention with reference to the schematic drawings. Advantages and features of the present invention will become apparent from the following description and claims. It is to be noted that the drawings are in a very simplified form and are not to precise scale, which is merely for the purpose of facilitating and distinctly claiming the embodiments of the present invention.
An embodiment of the present invention provides a single-base-station remote marine real-time dynamic positioning method, and specifically, as shown in fig. 1, fig. 1 is a flowchart of the single-base-station remote marine real-time dynamic positioning method in an embodiment of the present invention, where the method includes the following steps: firstly, receiving RTCM format data stream of a reference station in real time at a server side, and decoding the RTCM format data stream to obtain ephemeris data and real-time observation data of a current epoch. As shown in step S1 in fig. 1.
And then preprocessing the data, removing unqualified observation data, and simplifying the observation data by using a simplified correction number algorithm so as to obtain a simplified correction number. As shown in step S2 in fig. 1.
Specifically, the data preprocessing step after the observation data of the reference station are obtained comprises single-point positioning, pseudo-range observation value checking and rough error detection by a correlation analysis method. And the pseudo-range observation value checking refers to that the known reference station coordinates and satellite coordinates resolved in ephemeris are used for reversely deducing corresponding satellite distances, so that the pseudo-range observation values can be compared with the corresponding pseudo-range observation values, and if the difference between the pseudo-range observation values and the reversely deduced satellite distances is large, the observation values are considered to contain gross errors and should be discarded. The coarse difference detection by the correlation analysis method is to analyze coarse differences possibly contained in an observed value by using a coarse difference theory based on the correlation analysis after obtaining an observed value residual error sequence through single-point positioning, and abandon the observed value if detecting that the observed value contains the coarse differences. The gross error theory based on the correlation analysis is a set of gross error detection theory summarized by the people of break-in of Wuhan university and the like, so that the gross error theory belongs to the prior art.
The simplified processing step of the observation data by using the simplified correction number algorithm comprises the steps of deducting the calculated satellite-earth distance from the original observation value and eliminating the geometric distance change item generated by the satellite motion in the observation value; and then deducting the model correction quantity of troposphere delay in the observed value, reducing the numerical change of the original observed value as much as possible, and simultaneously reducing the absolute value of the pseudo-range observed value as much as possible, wherein the calculation formula is as follows:
wherein the content of the first and second substances,andis the corrected phase and pseudorange observations,andis the raw phase and pseudorange observations, the subscript r represents the reference station, the superscript s represents a satellite,andthe satellite earth distance, the receiver difference and the satellite clock difference calculated for the single-point positioning,the model for tropospheric delay is modified by an amount.
Finally, deducting the rounded integer part from the phase observed value and only keeping the decimal, so that the phase observed value only takes values from-0.5 to 0.5, and the calculation formula is as follows:
wherein, the first and the second end of the pipe are connected with each other,is a simplified observation of the phase [. Star ]]Denotes rounding the sum of x, λ is the observed phaseThe corresponding wavelength. In practice, integers areObserved value in phaseThe cycle can be used without cycle skipping and without recalculation each time.
The observations in the resulting simplified corrections include, after correction, pseudorange observationsAnd phase reduced observations
And step S3: and judging whether the simplified correction number calculated by the current epoch meets the requirement or not. If the corrected data meets the requirement, the corrected data is subjected to ASCII coding and then enters the observation data processing flow of the next epoch, as shown in step S4; otherwise, the simplified correction number of the current epoch is discarded and the observation data processing flow of the next epoch is entered.
Specifically, the criterion for determining whether the simplified correction calculated by the current epoch meets the requirement is to determine whether the absolute value of the pseudorange or the phase observation exceeds 1000, if not, the pseudorange or the phase observation meets the requirement, and otherwise, the pseudorange or the phase observation does not meet the requirement.
The ASCII encoding of the corrected numbers means that all the simplified corrected number information including the observation time of the corrected numbers, system mark, satellite number, simplified observed value, etc. are converted into binary systemThen the simplified nonce information in binary form is converted into ASCII character string form for transmission. For example, when 3 binary bits are used to represent the form of the system flag as 1 as 001, 5 binary bits are used to represent the form of the satellite number as 8 as 01000, and the information of the system flag and the satellite number is combined as 00101000, the conversion is made into ASCII characters as '40'. The specific coding method comprises that the 0 th bit to the 9 th bit of the binary correction number are used for storing the last three bits of the observation time of the simplified correction number, the 10 th bit to the 12 th bit are used for storing system marks, and the 13 th bit to the 17 th bit are used for storing satellite numbers; store information for each observed satellite starting at bit 18, 6 bits for satellite number, 5 bits for satellite ephemeris time, 1 bit for satellite ephemeris timeThe flag of whether to change, 21 bits, is used to store an observation of phase or pseudorange. After the binary number is obtained, every 8 bits can be converted into an ASCII character, and finally, less than 8 bits are converted into ASCII characters after 8 bits are filled with 0.
Step S5: and packaging and splitting the encoded simplified correction number into a plurality of short messages.
Specifically, the step of packaging and splitting the encoded simplified correction number comprises the step of dividing the simplified correction number information into a plurality of short messages, wherein each short message needs to be added with a check symbol to ensure that the messages can be recovered at a user side, and meanwhile, the size of each short message cannot exceed the maximum data volume which can be sent by a Beidou short message antenna at a service side at one time.
Step S6: and delivering the packaged data to a Beidou short message antenna of a server side for sending.
Specifically, three characteristics of the Beidou short message need to be noticed when the Beidou short message is used for transmitting the correction information. Firstly, one Beidou card only allows a user to broadcast a short message with the data volume not larger than 78.5 bytes at a time. Secondly, one Beidou card can only be used once in one minute, once a Beidou short message is sent, the Beidou card can sleep for one minute, and the time for sending the Beidou short message is very short and can be ignored. Thirdly, multiple Beidou cards can be fused to continuously broadcast the correction information, but a short message can be sent only in one second at the fastest speed. Based on the three characteristics, the Beidou card number needing to be fused is selected and the corresponding broadcasting rule is determined by combining with actual requirements. In the embodiment provided by the invention, the data volume of the simplified correction number information of one epoch is about 300 bytes, and considering that the time delay of the correction number information is preferably less than half a minute, 15 Beidou cards are selected and fused, and the correction number information is broadcast every 15 seconds, so that the delay is about 15-30 seconds. The calculation formula of the time delay is as follows:
m<t j <60+2m-k-(j-1)d(6a)
m<t i <2m+d(6a)
wherein, t j And t i Represents the time delay of the j-th and i-th simplified correction number information, and is 0<i<, j; n is the data size of the encoded simplified correction number information, and the unit is byte; k is the number of the merged Beidou cards. floor is a floor rounding operation. The formula gives a calculation formula of time delay of the correction information broadcast within one minute, and the time delay of the correction information broadcast after one minute is similar to the calculation formula. The broadcast rule of the correction number is that after one piece of correction number information is broadcast, the next piece of correction number information is broadcast again at an interval of d seconds until the jth piece of correction number information is sent.
Step S7: the Beidou short message antenna of the user side sequentially receives a plurality of Beidou short messages sent by the service side antenna, and the short messages are spliced again to form a simplified correction number after being coded and are delivered to the user side positioning software for use after being decoded.
Specifically, the step of re-splicing the received Beidou short messages into the coded simplified correction number by the user side comprises the steps of checking whether the received short messages belong to the same simplified correction number information or whether the short messages of the same simplified correction number information are missing or not by using a check symbol of each short message, splicing the short messages belonging to the same simplified correction number information according to the check symbol if the problem does not exist after checking, and obtaining complete coded simplified correction number information, or else, waiting until all the short messages of the simplified correction number information are received by the user side.
Step S8: the user positioning software needs to receive the RTCM format data stream of the mobile station and the code simplified correction number sent by the short message antenna at the same time. And reading the observation data of the ephemeris and the current epoch rover from the data stream, preprocessing the data in the same way, eliminating unqualified observation data, and decoding the encoded simplified correction number.
Specifically, the step of preprocessing the user side data comprises single point positioning, pseudo-range observation value checking and rough error detection of a correlation analysis method. And the pseudo-range observation value checking refers to that the approximate satellite distance corresponding to the satellite coordinate resolved in the ephemeris is reversely deduced by utilizing the predicted rover coordinate, so that the pseudo-range observation value can be compared with the corresponding pseudo-range observation value, and if the difference between the pseudo-range observation value and the reversely deduced approximate satellite distance is large, the observation value is considered to contain a gross error and should be discarded. The coarse difference detection by the correlation analysis method is to analyze coarse differences possibly contained in an observed value by using the correlation analysis method after an observed value residual sequence is obtained through single-point positioning, and discard the observed value if the observed value contains the coarse differences.
Step S9: and judging whether the simplified correction number is qualified or not. If the position is qualified, performing offshore real-time kinematic (ORTK) positioning, as shown in step S10; otherwise, only the single point positioning is performed, as shown in step S11. And finally, after the positioning result is spitted out, entering the observation data processing flow of the next epoch.
Specifically, the method for judging whether the simplified correction number is qualified or not at the user side is to calculate the difference between the observation time of the simplified correction number and the observation time of the observation data of the rover station, if the time difference is less than 1 minute, the simplified correction number is qualified, and if not, the simplified correction number is unqualified.
The ORTK positioning of the rover station is carried out based on the combination of dual-frequency phase of a GPS navigation system and a Beidou navigation system and an Ionosphere-Free (IF) combination of a pseudo range observed value, the method comprises the steps of constructing an inter-station differential observed value by using rover station observed data and a received simplified correction number, and the formula is as follows:
wherein the content of the first and second substances,andto simplify the differential phase between stations and the pseudorange observations,andis a simplified observation of the phase of the reference station and a corrected pseudorange observation,andfor the raw phase and pseudorange observations of the rover station,andapproximate satellite distance, receiver clock error and satellite clock error of the rover station calculated for single-point positioning,the model for the rover tropospheric delay is modified by an amount.
After the inter-station difference observation value is obtained, selecting a proper reference satellite, and carrying out inter-planet difference to obtain a double-difference observation value, wherein the formula is as follows:
wherein the superscript s represents the selected reference satellite and the superscript v represents any other satelliteAnd withRepresenting simplified double-differenced phase and pseudorange observations,and withRepresenting simplified post-station differential phase and pseudorange observations of satellite v.
Then, considering that the observed value has two frequencies, a linear combination can be performed on the dual-difference observed values of the two frequencies to obtain a dual-difference observed value of the IF combination, where the following formula is shown:
wherein the content of the first and second substances,and withDouble differential observation of phase and pseudoranges for IF combining 1 Frequency of the first frequency observation, f 2 For the frequency of the second frequency observation,anda dual differential observation of phase and pseudorange for the first frequency,anda dual differential observation of the phase and the pseudorange for the second frequency.
Because residual tropospheric delay is not considered, the only parameters to be solved based on the IF combined double-difference observations are the rover position parameters and the IF combined double-difference ambiguity parameters, an error equation as shown below can be obtained:
wherein the content of the first and second substances,is a double-difference distance, and comprises three unknown rover position parameters,is the wavelength of the narrow lane, c represents the speed of light,for the IF combining of the double-difference ambiguity parameters,andare the residual phase and pseudorange observations errors.
Writing the error equation in matrix form:
wherein phi IF And P IF Representing an observation vector consisting of a plurality of dual-differential observations of satellite phase and pseudorange, A being a coefficient matrix of rover position parameters, I m Is an m-order identity matrix, m is the number of ambiguity parameters, x represents the rover's position parameter vector, a represents the ambiguity parameter vector,and withIs an error vector formed by the residual errors.
The rover position parameter is different due to the movement of the rover every moment, but the ambiguity parameter does not change along with the time, so that the characteristic can be utilized to combine the observed value information of a plurality of moments for sequential solution. In the sequential solution, the calculation formula of the rover position parameter and the ambiguity parameter is as follows:
wherein the content of the first and second substances,andrespectively obtaining errors in prior of two frequency original phases and pseudo-range observed values; q dd The covariance matrix is a covariance matrix of double-difference observed values and is independent of frequency;andcovariance matrices of pseudo-range and phase double-difference observations of the IF combinations, respectively; the subscript k represents the time of day,and A k Coefficient matrixes respectively representing ambiguity parameter solutions at the k moments, rover position parameter solutions and rover position parameters;is a covariance matrix of the ambiguity parameter solution at time k;is a covariance matrix of the rover position parameter solution at the time k; when k =0, the signal is transmitted,anda zero vector or a zero matrix.
Preferably, the ORTK positioning of the rover station is different from the conventional RTK positioning, which needs to additionally consider the observation time inconsistency of the rover station observation data and the simplified correction number and the problems of serious marine multipath effect and special observation environment. Since the satellite clock differences cannot be eliminated by the inter-station difference due to the inconsistency between the observation data and the observation time of the simplified correction number, the accurate satellite clock differences at the respective observation times must be calculated by using the ephemeris of the satellites at the time of single-point positioning, and then subtracted from the original observation values as shown in equations (1 a) and (1 b). Furthermore, it must be ensured that the rover and the reference station use the same time satellite ephemeris for the calculation of the satellite clock difference. In the sea, the observation environment is different from the land, the multipath effect is obvious, the equipment needs to be arranged on a ship, and the ship often has some other equipment to interfere with the satellite signal, so that the rover observation data obtained in the environment often has a plurality of gross errors. For single gross errors, it can be better detected in single point positioning using correlation analysis. However, for two or more gross errors, because the number of redundant observations in satellite positioning is small, the effect of gross error detection is poor, and the situations of erroneous judgment and missed judgment often occur, at this time, because the ORTK positioning is based on sequential solution, the failure of gross error detection at a certain moment affects the parameter solution quality at all subsequent moments. In order to avoid the situation, the ORTK not only adds the correlation analysis method coarse difference detection in single-point positioning, but also utilizes pseudo-range double-difference observed values combined by IF (intermediate frequency) to carry out positioning and coarse difference detection in subsequent ORTK positioning, and checks the posterior-to-intermediate error of parameters obtained by resolving the final ORTK positioning. If the gross error detection fails, the error in the parameter after test is obviously larger and even exceeds the normal value by several orders of magnitude, and at the moment, the moment is skipped without updating the result into the parameter of sequential calculation, and the moment gives out the result of single-point positioning.
Compared with the prior art, the single-base-station long-distance offshore real-time dynamic positioning method provided by the embodiment of the invention at least has the following beneficial effects:
firstly, the single-base-station long-distance offshore real-time dynamic positioning method provided by the embodiment of the invention is carried out with the IF combined observed value, and then the influence of an ionized layer on positioning is not needed to be considered except for a medium-altitude area and a high-altitude area, theoretically, the positioning precision is only influenced by residual troposphere errors, so that the positioning result is more stable.
Secondly, the single-base-station remote-distance offshore real-time dynamic positioning method provided by the embodiment of the invention does not fix the narrow-lane ambiguity theoretically, can provide positioning service with equivalent precision to the fixed ambiguity within a range of dozens of kilometers away from a base station, and can provide sub-decimeter-level positioning service with slightly lower precision within a range of more than or even hundreds of kilometers away from the base station.
Thirdly, the single-base-station long-distance offshore real-time dynamic positioning method provided by the embodiment of the invention does not ignore the residual troposphere delay parameter in the zenith direction theoretically, thereby sacrificing the positioning accuracy in a certain elevation direction, improving the reliability of the positioning result and shortening the convergence time of the positioning result.
Fourthly, the single-base-station long-distance offshore real-time dynamic positioning method provided by the embodiment of the invention can solve the problem that the correction number information is inconsistent with the observation time of the observation data of the rover station, thereby prolonging the effective use time of the correction number information at a user terminal and reducing the frequency of the user terminal for the correction number information.
Fifthly, the invention solves the problems of inconvenience in maritime communication and incapability of transmitting correction number information by using the Beidou short message. Compared with the conventional satellite communication, the Beidou short message has lower cost. In addition, the invention also provides a simplified correction number algorithm and a corresponding coding method, thereby greatly reducing the requirement of the transmission of the correction number information on the communication bandwidth and enabling the transmission of the correction number information through the Beidou short message to be possible.
Sixth, the invention develops specific user-side rover positioning software for the special marine observation environment, and can avoid the situation that the observation values contain a plurality of gross errors to generate continuous influence on the positioning effect as far as possible, so that the positioning result of the rover is stable and reliable.
In summary, in the single-base-station long-distance marine real-time dynamic positioning method provided in the embodiment of the present invention, a service end receives a reference station RTCM format data stream in real time, and decodes the RTCM format data stream to obtain ephemeris data and current epoch real-time observation data. And preprocessing the data, and removing unqualified observation data. And then, simplifying the observation data by using a simplified correction number algorithm, thereby obtaining a simplified correction number. Then judging whether the simplified correction number calculated by the current epoch meets the requirement, if so, performing ASCII encoding on the correction number and entering the observation data processing flow of the next epoch; otherwise, the simplified correction number of the current epoch is discarded and the observation data processing flow of the next epoch is entered. And then packaging and splitting the coded simplified correction number into a plurality of short messages, submitting the short messages to a Beidou short message antenna of the service end for sending, sequentially receiving a plurality of Beidou short messages sent by the service end antenna through the Beidou short message antenna of the user end, splicing the short messages into the coded simplified correction number again, and submitting the coded simplified correction number to user end positioning software for use. The user positioning software needs to receive the RTCM format data stream of the mobile station and the code simplified correction number sent by the short message antenna at the same time. And reading the observation data of the ephemeris and the current epoch rover from the data stream, preprocessing the data in the same way, and removing unqualified observation data. Decoding the encoded simplified correction number, judging whether the simplified correction number is qualified, and if so, performing offshore real-time kinematic (Ocean-RTK, ORTK) positioning; otherwise, only single point positioning is carried out. And finally, after the positioning result is spitted out, entering the observation data processing flow of the next epoch. The invention solves the problem of inconvenient marine communication by using the Beidou short message; the problem that the Beidou short message communication bandwidth is too small and is not suitable for transmitting normal correction number information is solved by using a simplified correction number algorithm and a corresponding coding method; by utilizing the method of multiple coarse error detection and error detection after inspection, the continuous deterioration of the positioning effect is avoided as much as possible under the condition of multiple coarse errors, so that the positioning algorithm of the user terminal rover station can adapt to the special environment at sea.
The above description is only a preferred embodiment of the present invention, and does not limit the present invention in any way. It will be understood by those skilled in the art that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. A single-base-station remote offshore real-time dynamic positioning method is characterized by comprising the following steps:
and receiving the RTCM format data stream of the reference station in real time at the server side, and decoding the RTCM format data stream to obtain ephemeris data and real-time observation data of the current epoch. And preprocessing the data, and removing unqualified observation data. And then, simplifying the observation data by using a simplified correction number algorithm, thereby obtaining a simplified correction number.
Judging whether the simplified correction number calculated by the current epoch meets the requirement, if so, performing ASCII encoding on the correction number and entering an observation data processing flow of the next epoch; otherwise, the simplified correction number of the current epoch is abandoned and the observation data processing flow of the next epoch is entered.
And packaging and splitting the encoded simplified correction number into a plurality of short messages, submitting the short messages to a Beidou short message antenna of the service end for sending, sequentially receiving a plurality of Beidou short messages sent by the service end antenna by the Beidou short message antenna of the user end, splicing the short messages into the encoded simplified correction number again, and submitting the simplified correction number to user end positioning software for use.
The user positioning software needs to receive the RTCM format data stream of the mobile station and the code simplified correction number sent by the short message antenna at the same time. And reading the observation data of the ephemeris and the current epoch rover from the data stream, preprocessing the data in the same way, and removing unqualified observation data. Decoding the encoded simplified correction number, judging whether the simplified correction number is qualified, and if so, performing offshore real-time kinematic (Ocean-RTK, ORTK) positioning; otherwise, only single point positioning is performed. And finally, after the positioning result is spitted out, entering the observation data processing flow of the next epoch.
2. The single-base-station long-range offshore real-time dynamic positioning method of claim 1, wherein the step of preprocessing the reference station observation data and the user-side data comprises single-point positioning, pseudo-range observation checking and correlation analysis gross error detection. And the pseudo-range observation value checking refers to that the known reference station coordinates or the predicted user terminal rover station coordinates and satellite coordinates resolved in ephemeris are used for reversely deducing corresponding satellite distances so as to be compared with corresponding pseudo-range observation values, and if the difference between the pseudo-range observation values and the reversely deduced satellite distances is large, the observation values are considered to contain gross errors and should be discarded. The coarse difference detection by the correlation analysis method is to analyze coarse differences possibly contained in an observed value by using a coarse difference theory based on the correlation analysis after obtaining an observed value residual error sequence through single-point positioning, and abandon the observed value if the observed value contains the coarse differences.
3. The single-base-station long-range marine real-time dynamic positioning method of claim 1, wherein the step of simplifying the observation data by using a simplified correction algorithm comprises the steps of deducting the calculated satellite distance from the original observation value, and eliminating the geometric distance variation term generated by the satellite motion in the observation value; then deducting model correction of troposphere delay in the observed value, reducing the numerical change of the original observed value as much as possible, and simultaneously reducing the absolute value of pseudo-range observed value as much as possible, wherein the calculation formula is as follows:
wherein the content of the first and second substances,andis the corrected phase and pseudorange observations,andis the raw phase and pseudorange observations, the subscript r represents the reference station, the superscript s represents a satellite,andthe satellite earth distance, the receiver difference and the satellite clock difference calculated for the single-point positioning,the amount is modified for the model of tropospheric delay.
Finally, deducting the rounded integer part from the phase observed value and only keeping the decimal, so that the phase observed value only takes values from-0.5 to 0.5, and the calculation formula is as follows:
wherein the content of the first and second substances,is a simplified observation of the phase [. Star ]]Denotes rounding the sum of x, λ is the observed phaseThe corresponding wavelength. In practice, integers areObserved value in phaseThe cycle skip does not occur, and the cycle skip can be used all the time without recalculation every time.
The observations in the resulting simplified corrections include, after correction, pseudorange observationsAnd phase simplification of observed values
4. The method as claimed in claim 1, wherein the criterion for determining whether the simplified correction calculated by the current epoch meets the requirement is to determine whether the absolute value of the pseudorange or the phase observation exceeds 1000, if not, the simplified correction meets the requirement, otherwise, the simplified correction does not meet the requirement.
5. The single-base-station long-distance offshore real-time dynamic positioning method as claimed in claim 1, wherein the ASCII encoding of the correction numbers means that all the simplified correction number information, including the correction number observation time, system flag, satellite number, simplified observation value, etc., is converted into a binary form, and then the simplified correction number information in the binary form is converted into an ASCII character string form for transmission. For example, when 3 binary bits are used to represent the form of the system flag as 1 as 001, 5 binary bits are used to represent the form of the satellite number as 8 as 01000, and the information of the system flag and the satellite number is combined as 00101000, the conversion is made into ASCII characters as '40'. The specific coding method comprises that the 0 th bit to the 9 th bit of the binary correction number are used for storing the last three bits of the observation time of the simplified correction number, the 10 th bit to the 12 th bit are used for storing system marks, and the 13 th bit to the 17 th bit are used for storing satellite numbers; store information for each observed satellite starting at bit 18, 6 bits for satellite number, 5 bits for satellite ephemeris time, 1 bit for satellite ephemeris timeThe flag of whether to change, 21 bits, is used to store an observed value of phase or pseudorange. After the binary number is obtained, every 8 bits can be converted into an ASCII character, and finally, less than 8 bits are converted into ASCII characters after 8 bits are filled with 0.
6. The single-base-station long-distance offshore real-time dynamic positioning method of claim 1, wherein the step of packing and splitting the encoded simplified nonce comprises dividing the simplified nonce information into a plurality of short messages, each of which requires a check symbol to be added to ensure that they can be recovered at the user side, and at the same time, the size of each short message cannot exceed the maximum data amount that can be transmitted by the Beidou short message antenna at the service side at one time. Three characteristics of the Beidou short message need to be noticed when the Beidou short message is used for transmitting the correction information. First, one beidou card only allows a user to broadcast a short message with data size not greater than 78.5 bytes at a time. Secondly, one Beidou card can only be used once in one minute, once a Beidou short message is sent, the Beidou card can sleep for one minute, and the time for sending the Beidou short message is very short and can be ignored. And thirdly, multiple Beidou cards can be fused to continuously broadcast the corrected number information, but only one short message can be sent in one second at the fastest speed. Based on the three characteristics, the Beidou card number needing to be fused is selected and the corresponding broadcasting rule is determined by combining with actual requirements, so that the time delay of the correction information cannot influence the final positioning effect. The time delay of the correction count information is a time delay of the observation time of the simplified correction count information with respect to the observation time of the rover observation data.
7. The single-base-station long-distance offshore real-time dynamic positioning method as claimed in claim 1, wherein the step of re-splicing the received beidou short messages into the encoded simplified correction number by the user terminal includes checking whether the received short messages belong to the same simplified correction number information or whether the short messages of the same simplified correction number information are missing or not by using the check symbol of each short message, and after checking, if the above problem does not exist, splicing the short messages belonging to the same simplified correction number information in sequence according to the check symbol to obtain a complete encoded simplified correction number information, otherwise, waiting until all the short messages of the simplified correction number information are received by the user terminal.
8. The method of claim 1, wherein the determining at the user end whether the reduced correction is acceptable is by calculating a difference between an observation time of the reduced correction and an observation time of the rover observation data, wherein the reduced correction is acceptable if the difference is less than 1 minute, and the reduced correction is not acceptable otherwise.
9. The single-base-station remote offshore real-time dynamic positioning method as claimed in claim 1, wherein the ORTK positioning of the rover station is performed based on the combination of the dual-frequency phases of the GPS and Beidou navigation systems and the Ionosphere-Free (IF) of the pseudo-range observed value, and the method comprises the steps of constructing the inter-station differential observed value by using rover station observed data and the received simplified correction numbers, and the formula is as follows:
wherein, the first and the second end of the pipe are connected with each other,andto simplify the differential phase between stations and the pseudorange observations,andis a simplified observation of the phase of the reference station and a corrected pseudorange observation,andfor the rover's raw phase and pseudorange observations,and withApproximate satellite distance, receiver clock error and satellite clock error of the rover calculated by single-point positioning,the rover is modeled on the tropospheric delay.
After the inter-station difference observation value is obtained, selecting a proper reference satellite, and carrying out inter-planet difference to obtain a double-difference observation value, wherein the formula is as follows:
wherein the superscript s represents the selected reference satellite and the superscript v represents any other satelliteAndrepresenting simplified double-differenced phase and pseudorange observations,and withRepresenting simplified post-station differential phase and pseudorange observations of satellite v.
Then, considering that the observed value has two frequencies, a linear combination can be performed on the dual-difference observed values of the two frequencies to obtain a dual-difference observed value of the IF combination, where the following formula is shown:
wherein, the first and the second end of the pipe are connected with each other,anddouble differential observation of phase and pseudoranges for IF combining 1 Frequency of the first frequency observation, f 2 For the frequency of the second frequency observation,and withIs a dual differential observation of the phase of the first frequency and the pseudorange,and withA dual differential observation of the phase and the pseudorange for the second frequency.
Because residual tropospheric delay is not considered, the only parameters to be solved based on the IF combined double-difference observation value are the position parameter of the rover station and the IF combined double-difference ambiguity parameter, and an error equation as shown below can be obtained:
wherein the content of the first and second substances,is a double-difference earth distance, and comprises three unknown rover position parameters,is the wavelength of the narrow lane, c represents the speed of light,for the IF to combine the double-difference ambiguity parameters,andare the residual phase and pseudorange observations errors.
Writing the error equation in matrix form:
wherein phi IF And P IF Representing an observation vector consisting of a plurality of dual-differential observations of satellite phase and pseudorange, A being a coefficient matrix of rover position parameters, I m Is an m-order identity matrix, m is the number of ambiguity parameters, x represents the rover position parameter vector, a represents the ambiguityThe vector of parameters is then used to determine,andis an error vector formed by the residual errors.
The rover position parameter is different due to the movement of the rover every moment, but the ambiguity parameter does not change along with the time, so that the characteristic can be utilized to combine the observed value information of a plurality of moments for sequential solution. In the sequential solution, the calculation formula of the rover position parameter and the ambiguity parameter is as follows:
wherein, the first and the second end of the pipe are connected with each other,and withRespectively obtaining errors in prior of two frequency original phases and pseudo-range observed values; q dd The covariance matrix is a covariance matrix of double-difference observed values and is independent of frequency;andthe covariance matrixes of pseudo range and phase double-difference observed values of the IF combination are respectively; the subscript k represents the time of day,and A k Respectively representing ambiguity parameter solutions at the k moments, rover position parameter solutions and coefficient matrixes of rover position parameters;is a covariance matrix of the ambiguity parameter solution at time k;is a covariance matrix of a rover position parameter solution at the moment k; when k =0, the number of the bits is set to zero,andis a zero vector or a zero momentAnd (5) arraying.
10. The single base station long range marine real-time dynamic positioning method of claim 1, wherein the ORTK positioning of the rover station is different from the conventional RTK positioning, which requires additional consideration of the inconsistency between the observation data of the rover station and the observation time of the simplified correction number, the severe marine multipath effect, and the special observation environment. Since the satellite clock differences cannot be eliminated by the inter-station difference due to the inconsistency between the observation data and the observation time of the simplified correction number, the accurate satellite clock differences at the respective observation times must be calculated by using the ephemeris of the satellites during the single-point positioning, and then subtracted from the original observation values as shown in formulas (1 a) and (1 b). And, it must be ensured that the rover and the reference station use the same time satellite ephemeris for the calculation of the satellite clock error. In the sea, the observation environment is different from the land, the multipath effect is obvious, and the equipment needs to be arranged on a ship, and the ship often has some other equipment to interfere with the satellite signal, so that the rover observation data obtained in the environment often contains a plurality of gross errors. For single gross errors, it can be better detected in single point positioning using correlation analysis. However, for two or more gross errors, because the number of redundant observations in satellite positioning is small, the gross error detection effect is poor, and the situations of erroneous judgment and missed judgment often occur, at this time, because the ORTK positioning is based on sequential solution, the parameter solution quality at all subsequent times can be influenced by the failure of gross error detection at a certain moment. To avoid this, the ORTK not only adds correlation analysis coarse-difference detection in single-point positioning, but also uses the pseudorange double-difference observed value combined by IF to perform positioning and coarse-difference detection in subsequent ORTK positioning, and checks the post-check medium error of the parameter obtained by final ORTK positioning solution. If the gross error detection fails, the error in the parameter after verification is obviously larger and even exceeds the normal value by several orders of magnitude, and at the moment, the moment is skipped without updating the result into the parameters of sequential calculation, and the moment gives out the result of single-point positioning.
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